Interstellar puzzle based on Graph Theory
treksit.com
treksit.com
Also (Chrome on MacOS) if you drag a node to the border and it stops, the node is now stuck to the mouse and you have to click to drop it.
My one bit of feedback would be that you should make it get more difficult more quickly. I lost interest and stopped playing it because it didn't seem to be getting substantially harder, it was just basically the same thing over and over again, but the design of the puzzle is good and means it should be easy to make more difficult levels.
Perhaps you could have a difficulty selector so that the player can advance at his own pace.
You could also introduce a little twist after a while where some of the points are fixed in space, and you must rearrange the others around the fixed ones, instead of being able to move all of them.
You could potentially also make different types of edge (e.g. red edges in addition to the green edges), and for example a red may cross a green, but not another red.
I was surprised there was only 20 puzzles, and was a bit confused where the next button had gone until I had realised that was it... but then I learned a while ago that something like only 10% of people complete the games they buy, so from that perspective if you care more about the 90% then it wont make any difference. I'm probably in the 10% who came from that unreal/HL generation used to blasting through long games with lots of medium difficulty puzzles who don't expect to be walked through everything, but that's now the minority.
NP-hard puzzles otoh, are hopeless for hard instances and general algorithms. Both the designer has to give it more thought on making instances that are not worst-case, and you have to rely not on general-case algorithms but an increasing set of heuristics and intuition to solve. Brute force is completely hopeless.
The same goes for two-player games. If the game can be solved in polynomial time, one of the players will find a trick (the polynomial time algorithm essentially) to always win (or depending on the game always draw).
Pic: https://en.m.wikipedia.org/wiki/File:Complete_graph_K5.svg